Molecular and supramolecular devices e.g. molecular switches, photo-sensible complexants or molecular wires are currently of utmost interest, because they provide a novel approach for performing a variety of different tasks, like for instance photo-induced ion transport, photo-induced catalysis or electron transport within molecular wires. Basically, the function performed by a molecular or supramolecular device results from elementary properties performed by the components, such as photoactive, electroactive or ionoactive components, depending on whether they could operate with photons, electrons or ions. When it comes to photo-active molecular devices, usually a photo-sensitive component, like a disulfide bridge ((R—S—S—R′) or an azo-component (R—N═N—R′) within the underlying photo-sensitive molecule is involved. Upon irradiation with light of an appropriate wave-length, a cis/trans isomerisation can be induced within the photo-sensitive molecule, thus leading for instance to markedly different complexing properties of the entire molecule. As a result, complexation and transport of suitable guests (e.g. ions) can be performed and stopped under the influence of light. Examples of known molecular and supramolecular devices, e.g. photo-induced ion transport systems are described in F. Vögtle, Supra-moleculare Chemie, Teubner Studienbücher, Stuttgart 1992.
Another field of interest in connection with supramolecular or molecular devices is related to data processing by means of optical computing. Usual data processing is essentially performed with magnetic layers and/or digital electronic computers consisting of a large collection of interconnected switches, gates and memory elements called “flip-flops”. Logic operations are performed by controlling the flow of electrons between these various components. Optical computers also use switches, gates and flip-flops in their logic operations, but the design of these devices are very different. The purpose of a switch is to make or break a connection between one or more transmission paths. If a switch controls the connection from just one path to another path, it is called a 1×1 switch. Other possibilities include 2×2, n×n, n×m switches whereby n and m could be any integer.
In optical computers, switches can be built from modulators using opto-mechanical, electro-optic, acusto-optic, magnetic-optic and other techniques. A well-known example represents the Mach-Zehnder interferometer in which the refractive index of one leg is electro-optically controlled and which is used as a 1×1 optical switch. By modulating the relative phase of the divided wavefronts as they pass through the interferometer, they can be constructively or destructively recombined at the output, thus creating an on-state or an off-state.
Another known optical switching design is the directional coupler which represents a 2×2 switch. Again, the electro-optic control of the refractive index of these devices shifts them between two states: cross and bar. Further modulators are known, whereby the on/off state is provided by liquid crystals or acousto-optic switches.
The above described optical switches are electrically or magnetically controlled. With the help of certain non-linear optical effects, all optical switches can be constructed as well. For example, by using the optical Kerr effect, it is possible to transform the above mentioned Mach-Zehnder interferometer into an all-optical switch.
Another feature of data processing is data storage by optical disks and holograms. The information on optical disks (e.g. CD-disks) is stored on the underside of said disk in a digital form represented by pits of different lengths embedded in an aluminum-coated layer protected by a surface coating of plastic. To read the information off the spinning disk, CW-light from a low power diode laser is tightly focused onto the pits by a short-focal-length objective mounted on a movable read head. Thus, the information stored by a binary code consisting of pits of different lengths can be repeatedly read-out.
An intense search for novel materials is currently under way, whereby said materials are intended to provide the possibility for information storage and processing. The underlying material must be modifiable by an external source so to apply an erasable or durable distribution of physical properties that could be determined by appropriate technical means for read-out purposes. Said physical properties could comprise among others optical properties, e.g. the refraction index, magnetic properties or mechanical properties like the different length of pits (e.g. in CD-disks).
One aspect of the present invention was to provide a novel material, i.e. novel chemical compounds, which displays two different states that can be determined for read-out purposes.
A further aspect of the present invention was to provide a method of information storage and data processing using said novel chemical compounds.
Still a further aspect of this invention was to provide novel photo-sensitive (4n)-annulene systems that are capable of thermal or photochemical double-bond shifts thus providing the possibility of switch from one conjugation state to another under the influence of an external source, e.g. light or heat.
Another further aspect of the present invention was to provide a method for preparing novel (4n)-annulenes that are capable of thermal or photochemical double-bond shifts.